C. elegans HCF-1 is a functional homolog of the human herpes simplex virus (HSV) host-cell factor HCF-1, which forms a complex with the HSV protein VP16 and a second cellular protein, Oct-1, upon HSV infection to promote HSV IE-gene transcription. In mammals, it has been demonstrated that HCF-1 is an abundant chromatin-associated protein that regulates multiple steps of the cell division cycle and associates with Trithorax-related histone H3 lysine 4 methyltransferase and Sin3 histone deacetylase. To elucidate the role of C. elegans HCF-1 in development, we examined the expression profile of
hcf-1 and the phenotypes of
hcf-1 mutants. Using semi-quantitative RT-PCR we show that
hcf-1 is expressed continuously throughout the life cycle of worms and is present in both somatic and germline tissues. For phenotypic analysis, we characterized two loss-of-function alleles,
pk924 and
ok559, of
hcf-1.
hcf-1(
pk924) was obtained by PCR-screening of a deletion library from the Plasterk lab (1). It contains a 1455 bp frame-shift deletion that creates a nine-codon out-of-frame extension after the first 106
hcf-1 codons, predicting a 115-amino-acid peptide. On the other hand,
hcf-1(
ok559) was obtained from the C. elegans Gene Knockout Consortium (Oklahoma Medical Research Foundation, Oklahoma City, OK). It contains an 1120 bp in-frame deletion that encodes a 454 amino acid protein missing nearly the entire VP16-interacting Kelch domain (residues 17 to 344 of 782). Previous phenotypic analysis revealed that
hcf-1 mutants of both alleles have a smaller brood size, are cold-sensitive embryonic lethal and have a higher incidence of males (Him) (1). Recently we have extended the phenotypic analysis of
hcf-1 mutants. Our data show that
hcf-1 worms grow slower and live longer than N2. In addition, immunohistological analysis reveals that
hcf-1 mutations affect histone H3 modification.
hcf-1 embryos have reduced levels of histone H3 lysine 4 and 27 methylation and serine 10 phosphorylation (1). These characteristics are consistent with the role of HCF-1 as a global transcriptional regulator that participates in multiple developmental processes in C. elegans. (1)Lee S, Horn V, Julien E, Liu Y, Wysocka J, Bowerman B, Hengartner MO, and Herr W: HCF proteins play conserved roles in cell division and histone modification. Manuscript in preparation. #The first two authors contributed equally to this study.